Pressurized gas supplies are utilized in a variety of industries and in conjunction with a variety of gas-consuming devices, such as gas actuators and pneumatic isolators of the type employed within optical benches and magnetic resonance imaging machines. As a specific example, a pressurized gas supply may be deployed onboard a missile and utilized to adjust the position of control surfaces (e.g., the missile's fins), to open collapsible wings, or to drive one or more rotating gas bearings. When deployed onboard a missile, or utilized in other such applications wherein available space is limited, the pressurized gas supply may include a pressurized vessel (e.g., a metal tank) containing gas under extreme pressures; e.g., 4,000 pounds per square inch absolute (psia) to 9,000 psia or more. A pyrotechnic valve and a pressure regulator are fluidly coupled between the pressurized vessel and the gas-consuming device. The pyrotechnic valve normally prevents the release of pressurized gas from the pressurized vessel. To initiate operation of the pressurized gas supply, a charge within the pyrotechnic valve is ignited. This drives a pin through the wall of a gas supply tube permitting gas flow from pressurized vessel, through the valve, and to the pressure regulator. The pressure regulator then reduces the pressure of gas to a predetermined output pressure suitable for driving the gas-consuming device.
To operate certain gas-consuming devices in a reliable manner, it is desirable for a pressurized gas supply to provide gas output at a consistent mass flow rate and temperature. However, conventional pressurized gas supplies, and specifically conventional pressurized gas supplies wherein the gas output pressure is significantly less than the gas reservoir pressure, often fail to provide a consistent mass flow rate due to variations in temperature and corresponding variations in density of the output gas. Depending upon the species of gas contained within the pressurized vessel, and depending upon the operational temperature range and pressure range of the pressurized gas supply, the pressurized gas may heat or cool upon expansion across the pressure regulator (an occurrence commonly referred to as the “Joule-Thomson effect” or as the “Joule-Kelvin effect”). In addition, as gas is released from the pressurized vessel, the gas held within the pressurized vessel may continually cool due to the work done by the gas in the vessel to expel gas therefrom. Significant excursions in gas temperature may consequently occur over the operation of the pressurized gas supply resulting in undesirable fluctuations in gas density and, therefore, in mass flow rate. As a further disadvantage, if the temperature of the output gas decreases significantly, water and other contaminants entrained in the gas stream and on surfaces in contact with the gas stream may freeze, restrict gas flow, impede operation of the gas regulator or otherwise impact the performance of the gas-consuming device in an undesirable manner.
Accordingly, it is desirable to provide an isothermal gas supply for use in conjunction with certain gas-consuming devices (e.g., a gas bearing) that minimizes temperature excursion of the output gas (or gases) to maintain a substantially constant gas density and, therefore, a substantially constant mass flow rate. More generally, it is desirable to provide a pressurized gas supply that achieves a desired gas output temperature substantially equivalent to or greater than the starting temperature of the gas (or gases) held within the pressurized gas reservoir. It is also desirable to provide a method for minimizing the temperature deviation of gas or gas mixture released from a pressurized gas supply. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and this Background.